LU-814 tests: remove leading spaces from $WRITE_DISJOINT

LU-814 tests: remove leading spaces from $WRITE_DISJOINT

In functions.sh, the WRITE_DISJOINT variable is defined as follows:

    WRITE_DISJOINT=${WRITE_DISJOINT:-\
        $(which write_disjoint 2> /dev/null || true)}

This will assign WRITE_DISJOINT with a value leading with spaces,
which causes "[: too many arguments" issue while checking the
variable. The PARALLEL_GROUPLOCK variable also has the same issue.
This patch fixes it.

Signed-off-by: Yu Jian <yujian@whamcloud.com>
Change-Id: I424af2acd4ef79ea67830010d17b6904769c2ca4
Reviewed-on: http://review.whamcloud.com/2866
Tested-by: Hudson
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>